1. Field of the Invention
The present invention relates to a composite thin film recording/reproducing head integrally comprising a magneto-resistance effect thin film reproducing head (hereinafter referred to as "MR thin film reproducing head") having a magnetoresistance effect element (hereinafter referred to as "MR element"), and an inductive thin film recording head.
2. Description of the Prior Art
A recording medium of a discrete track type having discrete tracks formed by removing portions of the magnetic layer between the adjacent tracks to increase recording density is used as a magnetic recording medium or a magneto-optic recording medium. Recording density on an ordinary high-density recording medium, such as a hard disk, is in the range of 4000 tpi (tracks per inch) to 5000 tpi. Therefore, the track pitch is in the range of about 5 to about 6 .mu.m and the track width is on the order of 3 .mu.m. If such a high-density recording medium is provided with a continuous magnetic layer, relatively large noise, i.e., what is known as edge noise, is generated by the high-density recording medium, particularly, by portions of the high-density recording medium other than the tracks in reproducing recorded signals from the high-density recording medium. The edge noise is attributable mainly to noise of unstable phase written in the recording medium during recording operation by a portion of the recording head at a distance from the recording gap. Therefore, it is desirable to use a recording medium of a discrete track type for high-density recording.
The recording medium of a discrete track type is formed, for example, by forming a magnetic layer over the entire surface of a substrate having the shape of a disk by sputtering or evaporation, and subjecting the magnetic layer to a photolithographic process or the like to form a magnetic layer of a pattern of concentric circles or a spiral curve.
In recording signals on or reproducing recorded signals from the recording medium 23 by, for example, a floating magnetic head, a magnetic head 30 attached to a surface of a floating slider 31 facing the recording medium 23 is kept afloat over the recording tracks 21 of the recording medium 23 with a small gap between the magnetic head 30 and the surface of the recording medium 23 by air currents produced by the rotating recording medium 23 as shown in FIG. 6.
Various magnetic heads have been developed. For example, a MR thin film magnetic head having excellent shortwave sensitivity is used often as the reproducing magnetic head of the magnetic recording/reproducing head of a hard disk drive. Various composite thin film recording/reproducing heads each comprising a conventional inductive thin film recording head and a MR thin film reproducing head have been proposed.
Referring to FIG. 7 showing a composite MR/inductive thin film recording/reproducing head, a first magnetic layer 3 and a second magnetic layer 4 serving as shields for shielding a MR element 1 are formed respectively on the opposite sides of the MR element 1 on a floating slider or a base 6 attached to a floating slider so as to face the air bearing surface 7 of the composite MR/inductive thin film recording/reproducing head facing a magnetic recording medium, and nonmagnetic insulating layer 8 forming a recording magnetic gap, and a third magnetic layer 5 are formed over the first magnetic layer 3 and the second magnetic layer 4 so as to face the air bearing surface 7. A spiral head coil 2 is formed so as to surround the magnetically coupled back portions of the second magnetic layer 4 and the third magnetic layer 5. The second magnetic layer 4 and the third magnetic layer 5 constitute a recording head.
A front electrode 15 is formed near the MR element 1 on the side of the air bearing surface 7, and a back electrode 16 is formed on the other side of the MR element 1 to detect signal magnetic fields created by the recording medium facing the air bearing surface 7. A bias magnetic field is applied to the MR element 1 by a bias conductor 18.
Thus, a MR thin film magnetic head of what is known as a shield type having the MR element 1 formed between the first magnetic layer 3 and the second magnetic layer 4 is formed and an inductive magnetic head consisting of the second magnetic layer 4, the third magnetic layer 5, and the head coil 2 provided on a magnetic path including the second magnetic layer 4 and the third magnetic layer 5 is formed. The second magnetic layer 4 serves as a shield for the MR element in reproducing operation and as an inductive core in recording operation.
In the conventional composite MR/inductive thin film magnetic recording/reproducing head thus constructed, the width of the MR element 1 defining the track width W.sub.TM of the MR magnetic head, and the width of the third magnetic layer 5 defining the track width W.sub.TI of the inductive magnetic head are approximately equal to each other as shown in FIG. 8, and the optimization of the design of the MR/inductive thin film magnetic recording/reproducing head has been desired.